The invention relates to a method and a device for determining the sharpness of cutting edges of chopper blades at a rotationally driven chopper drum of a chopping assembly of a forage harvester, comprising a shear bar and a sharpening device having a sharpening stone for resharpening the chopper blades.
Document DE 10 2009 029 675 A1 discloses a device for determining the sharpness of chopper blades that can be moved with respect to a shear bar. The device comprises a sensor that directly or indirectly detects the effective cutting forces and an evaluation device connected to the sensor. The evaluation device integrates the measurement values of the sensor over time in order to generate information regarding the sharpness of the chopper blades. The basic idea is that blade wear correlates with the integral with respect to time of the cutting forces or the cutting energy. Therefore, a quantity that is dependent on the cutting forces that are effective while the crop is being chopped is measured by way of the sensor and a signal that is dependent on the quantity is integrated as a function of time by an evaluation device in order to generate information on the sharpness of the chopper blades.
It is a very difficult undertaking, however, to determine the cutting forces at a rotating chopper drum in the presence of very different loads, with sufficient accuracy, due to the continuous fluctuations of the throughput of mass.